Population-based estimates of the incidence, prevalence, morbidity and mortality of Alzheimer's disease for the U.S. have not been available. A study has recently been completed for the entire population of Rochester, Minnesota where the incidence of Alzheimer's disease has been estimated. This is the first study of its kind in the U.S. Another study to estimate the prevalence of "severe dementia" in a population with equal proportions of black and white Americans has also been completed and published. National mortality data for the entire U.S. for the period 1971, 1973-1978 for Alzheimer's disease and related diagnoses has also been analyzed for the first time and recently published. Analytic studies to determine risk factors for Alzheimer's disease are being conducted. A case-control study of late-onset Alzheimer's disease has been completed in Denver, Colorado. Another large-case-control study of Alzheimer's disease is in progress in White Plains, New York. A multi-center case-control study has also been completed in Italy. Since this study utilized a similar protocol to that used in the U.S., international comparisons are possible. A historical review of the distinction between "Alzheimer's disease" and "senile dementia" has been done. Projections for the prevalence of senile dementia in the year 2000 for several developed countries have been developed. An attempt has been made to evaluate and improve instruments used in case-control studies of dementia.